Multiple spool turbocharger

Abstract

Systems and methods for a multiple spool engine turbocharger are described. In one example approach, a multi-spool turbocharger comprises a compressor including a plurality of counter-rotating compressor spools and a turbine including a plurality of counter-rotating turbine spools.

The invention claimed is: 
     
       1. A method for operating a multiple spool turbocharger in an engine, comprising:
 counter-rotating first and second compressor spools and first and second turbine spools of the turbocharger; 
 during a first condition, wherein the first condition is a low engine load and/or speed operating condition, supplying compressed air from the first compressor spool to the engine and bypassing the second compressor spool; 
 during a second condition, wherein the second condition is a high engine load and/or speed operating condition, supplying compressed air from the second compressor spool to the engine and bypassing the first compressor spool; and 
 during a third transient condition, wherein the third transient condition is a tip-in or tip-out, supplying compressed air from both the first and second compressor spools to the engine. 
 
     
     
       2. The method of  claim 1 , wherein the first compressor spool is a low pressure spool and the first condition is a low engine speed operating condition. 
     
     
       3. The method of  claim 2 , wherein the second compressor spool is a high pressure spool and the second condition is a high engine speed operating condition. 
     
     
       4. The method of  claim 3 , wherein the first compressor spool is coupled to the second turbine spool via a first shaft rotatable in a first direction and the second compressor spool is coupled to the first turbine spool via a second shaft rotatable in a second direction the same or opposite the first direction. 
     
     
       5. The method of  claim 3 , wherein the first compressor spool is axial, the second compressor spool is radial, the first turbine spool is radial, and the second turbine spool is axial. 
     
     
       6. The method of  claim 3 , wherein the first compressor spool is radial, the second compressor spool is axial, the first turbine spool is axial, and the second turbine spool is radial. 
     
     
       7. The method of  claim 3 , wherein at least one of the first compressor spool, the second compressor spool, the first turbine spool, and the second turbine spool is a mixed-flow spool. 
     
     
       8. The method of  claim 3 , wherein each compressor spool and each turbine spool includes a bypass configured to direct gas flow around the respective spool. 
     
     
       9. The method of  claim 3 , wherein the turbocharger does not include guide vanes positioned between subsequent compressor spools or subsequent turbine spools.